It has been common practice to use fillers in polymers to produce a large variety of articles. Such articles contain a range of fillers such as, for example, highly stable and color-fast pigments, activated carbon sorbents, ion exchange resins, and fine silver particles for photographic films.
U.S. Pat. No. 2,947,646 (Devaney et al.) discloses colloidal dispersions of metals in plastics which are prepared by depositing a thin coating of metal onto finely powdered plastic, working the metal-coated plastic powder into a plastic state, the working resulting in fragmentation of the metal coating into very small metallic particles, and fabricating into the final shape.
U.S. Pat. No. 3,082,109 (Devaney et al.) discloses colloidal dispersions of metals in plastic which are prepared by incorporating into plastic metals which melt at or below the temperature of the metal rolls used for compounding the plastic material, compounding sufficiently to disperse the melted metals throughout the plastic, and fabricating into the final shape.
British Pat. Specification No. 1,100,497 describes the production of polymer fibers from polymer solutions wherein a solution of the polymer is formed at an elevated temperature, below the decomposition temperature of the polymer, in at least one non-polymeric compound which dissolves the polymer at the elevated temperature and which does not dissolve the polymer at a lower temperature and the solution is extruded downwardly through a spinneret into unheated air which cools the solution to the lower temperature causing separation of the polymer from the solvent to form a fiber. The fiber may contain fillers such as sulfur, carbon black, or an ion exchange resin.
M. C. Williams and A. L. Fricke, "Phase Separation Spinning of Polypropylene," SPE Journal, 28, Oct. 1972, p. 51, describe a method of making porous fibers by spinning a hot solution of polypropylene in naphthalene, allowing the spun solution to cool to solidify the fiber and effect phase separation of polypropylene and naphthalene, and removing the naphthalene by extraction with diethyl ether. Williams and Fricke suggest that this technique could possibly be used to produce fibers with high filler contents by mixing solid fillers into the spinning solution.
U.S. Pat. No. 3,351,495 (Larsen et al.) discloses a battery separator comprising a microporous sheet of a specified polyolefin. The battery separator, which preferably contains a homogeneous mixture of 8 to 100 volume percent of polyolefin, 0 to 40 volume percent plasticizer, and 0 to 92 volume percent inert filler material, is prepared by blending the components and then fluxing the blend in a conventional mixer such as a Banbury mixer or melt homogenizing the blend in a conventional two roll mill, forming the composition into sheet form, and extracting at least a portion of the inert filler and/or plasticizer.
U.S. Pat. No. 4,650,730 (Lundquist et al.) describes a battery separator having at least two plies, each in the form of a microporous sheet, at least one ply, formed from a polymeric composition comprising a polymer and, optionally, plasticizers, stabilizers, antioxidants, and the like but substantially no particulate filler and being capable of transforming to a substantially non-porous membrane at a temperature between about 80 and 150.degree. C., and at least one ply, formed from a polymeric composition comprising a polymer and, optionally, plasticizers, stabilizers, antioxidants, and the like and preferably contains a large amount (greater than 20) weight percentage of solid, particulate filler.
U.S. Pat. No. 3,745,142 (Mahlman et al.) describes a process for preparing highly filled polyolefins which comprises preparing a crystallizable olefin polymer having a specified particle size, adding to the olefin polymer about 50 to 1900%, based on the weight of olefin polymer of a solid, particulate, inorganic filler material which is insoluble in the olefin, which is solid at the melting point of the olefin polymer and which is in the form of particles of about 0.1 to 25 microns, shaping the resultant polymer-filler blend, and fusing the olefin polymer to from a continuous phase. The highly filled compositions can be prepared simply by adding the particulate inorganic filler directly into a dispersion, either aqueous or organic, of the olefin polymer and agitating to make the total dispersion uniform.
British Pat. Specification No. 1,327,602 (Hercules) describes a process for preparing filled olefin polymers containing about 35 to 90% by weight of a particulate, inert, inorganic filler comprising extruding a substantially homogeneous mixture of polymer, filler and 25 to 75% by weight of the homogeneous mixture of hydrocarbon wax, which acts as a low viscosity diluent for the polymer, to form a shaped structure, cooling the extruded blend to form a continuous polymer phase, extracting the wax, and recovering the filled structure in the shape desired.
U.S. Pat. Nos. 4,342,811 and No. 4,550,123 (Lopatin et al.) describe open-celled microporous sorbent-loaded textile fibers and films prepared by forming a melt blend, of the sorbent particles, the polymer and a selected diluent, e.g., in a batch-type blender such as a Sigma blade mixer or blending extruder such as a twin-screw compounding extruder, spinning or extruding and drawing down the fiber or film, and extracting the diluent.
U.S. Pat. No. 4,562,108 (Miyake et al.) describes a heat-retaining moisture-transmissible water-resistant fabric having a fibrous substrate, a discontinuous polymer layer or a polymer layer having a multiplicity of interconnecting fine pores, and a polymer layer containing 15 to 70 weight percent, based on the weight of the polymer, of heat ray-reflecting fine metal pieces and having interconnecting fine pores. Alternatively, a specified microporous film layer may be interposed between the polymer layers. The metal-containing layer is prepared by solvent casting the polymer after simple mixing with an aluminum paste.
In addition it has been known for a long time to use dyes and pigments in polymers for coloration. Products made using this art use commercially available pigment dispersions to avoid pigment agglomeration and the articles formed are usually of non- porous polymers. See D. Bennett, Nonwoven World, 2, Nov. 1987, p. 58.
Metal or metal oxide filled polymeric fabrics for X-ray absorption have been widely used to construct personal protective garments for a number of years. U.S. Pat. No. 3,514,607 describes composite shields against low energy X-rays which are sheets of a carrier material containing tin, antimony, iodine, barium, or a combination thereof and lead. The carrier material may be flexible, e.g., a plastic or rubber material, or rigid, e.g., a plastic or a building material. The minimum content of carrier material needed to yield materials with acceptable mechanical strength is 16% by weight.
U.S. Pat. No. 4,619,963 and No. 4,485,838 (Shoji et al.) describe a radiation shielding composite sheet material of melt-spun lead fibers of more than 99% purity, and containing 50 to 500 ppm tin, of a mean length of 0.5 to 1.3 mm which are embedded in a synthetic resin, such that the composite sheet has a specific gravity greater than 4.0. The sheet material can be formed by melt-spinning the tin-containing lead fibers at a diameter below 60 microns, cutting the fibers to a length of 0.5 to 1.3 mm in length, blending the fibers with a thermoplastic resin, e.g., in a Banbury mixer, and pressing the blend between rolls to form a sheet. Efficacy data is given comparing these constructions to powder filled composites made by the same process. The powder filled composites can be made with up to 75 weight percent lead and can absorb X-rays up to 60 percent as well as crystalline lead foil. The fiber filled composites can be made with up to 85 weight percent lead and absorb with 80 percent the efficiency of lead foil. Lead filler levels of 75 and 85 weight percent are 23 and 35 volume percent respectively.
U.S. Pat. No. 4,247,498 (Castro) discloses microporous polymers characterized by a relatively homogeneous, three-dimensional cellular structure having cells connected by pores of smaller dimension. The microporous polymers are prepared from thermoplastic polymers by heating a mixture of the polymer and a compatible liquid to form a homogeneous solution, cooling the solution under non-equilibrium thermodynamic conditions to initiate liquid-liquid phase separation, and continuing the cooling until the mixture achieves substantial handling strength.
U.S. Pat. No. 4,539,256 (Shipman) discloses a microporous sheet material characterized by a multiplicity of spaced randomly dispersed, equiaxed, non-uniform shaped particles of the thermoplastic polymer, adjacent thermoplastic particles connected to each other by a plurality of fibrils of the thermoplastic polymer. The sheet materials are prepared by melt blending crystallizable thermoplastic polymer with a compound which is miscible with the thermoplastic polymer at the melting temperature of the polymer but phase separates on cooling at or below the crystallization temperature of the polymer, forming a shaped article of the melt blend, cooling the shaped article to a temperature at which the polymer crystallizes to cause phase separation to occur between the thermoplastic polymer and the compound.
U.S. Pat. No. 4,726,989 (Mrozinski) discloses microporous materials incorporating a nucleating agent made by melt blending a crystallizable thermoplastic polymer with a nucleating agent which is capable of inducing subsequent crystallization of the thermoplastic polymer and with a compound which is miscible with the thermoplastic polymer at the melting temperature of the polymer but phase separates on cooling at or below the crystallization temperature of the polymer, forming a shaped article of the melt blend, cooling the shaped article to a temperature at which the nucleating agent induces the thermoplastic polymer to crystallize so as to cause phase separation to occur between the thermoplastic polymer and the compound.